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From: | Marcus Müller |
Subject: | Re: [Discuss-gnuradio] uhd_sink+uhd_source VS virtual_sink+virtual_source |
Date: | Tue, 03 Nov 2015 15:49:46 +0100 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 |
Hi Ekko, >difference between uhd_sink+uhd_source with virtual_sink+virtual_source uhd_sink / _source talk to radio hardware, virtual sink and source are just "invisible" GRC connections, and simply talk to the block that is attached to them. > in this grc when i use virtual_sink+virtual_source,the ber is zero obviously, because it's simply a direct connection, no noise, hence, no errors. > but when i use uhd_sink+uhd_source, and i connect the B200's tx and rx port with a RF wire. but the ber is not zero. Real world radios have noise (and other imperfections), and hence there's bit errors. That's the core problem of digital communications, and has been for the last couple of decades. > how can i use uhd_sink+uh_source just like virtual_sink+virtual_source You can't. One reproduces perfectly, the other is the real RF world. Getting information across the wireless channel without error is what science has been working on, and since Shannon we know that you can not achieve a transmission with arbitrarily low BER over a channel with limited SNR at arbitrary speed. Every real channel has limited SNR. What you do is apply your signal processing and communication theory skills to counteract the effects of the channel, check correctness and correct errors (if possible), possibly make the sender retransmit etc; but you will never break Shannon's limits. Best regards, Marcus On 11/03/2015 01:58 PM, chai E wrote:
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